Delay stabilizing system

Abstract

A system for stabilizing the amplitude and, thus, the delay of a signal pulse subsequent to the first interrogating signal pulse to a transponder used in a range measurement system. AGC level in the transponder is set responsive to the first interrogating pulse and is held for a time period encompassing the subsequent pulse.

What is claimed is: 
     
       1. A method for stabilizing delay of a second pulse in a transponder when a first pulse of equal amplitude to that of the second pulse and the second pulse are sequentially present in at least a single pulse train in a receiver of the transponder, the method comprising the steps of: measuring the amplitude of the first pulse in the receiver of the transponder;   controlling gain of the receiver as a function of said measured amplitude, said gain being held constant over a period of time including said second pulse;   detecting a preset threshold level of only the second pulse at an output of said receiver; and   triggering a transmitted signal from the transponder responsive to said threshold detection.   
     
     
       2. The method according to claim 1 wherein each of the pulse trains is derived from a single input pulse and further comprises the step of: generating the second pulse within the receiver.   
     
     
       3. The method according to claim 2 wherein said generating step further comprises: a unity gain delay circuit, said unity gain delay circuit having an input driven by the first pulse.   
     
     
       4. The method according to claim 1 further comprising the steps of: delaying the first pulse in the receiver in a delay circuit, the delay circuit having a gain equal to one, the second pulse being produced at the output of said delay circuit.   
     
     
       5. The method according to claim 1, 2, 3 or 4 wherein the second pulse is generated by passing the first pulse through a surface acoustic wave device and an amplifier, the second pulse having an amplitude equal to the first pulse. 
     
     
       6. In a range measurement system comprising a radar and a transponder wherein the transponder is interrogated by a series of pulse trains from the radar, each of the pulse trains comprising at least a first pulse having an amplitude, an improvement in the transponder comprising in combination: means for sensing the amplitude of the first pulse of each of said series of pulse trains;   means for controlling the gain of a receiver in the transponder, said controlling means being responsive to said sensed amplitude of the first pulse, to establish a constant output signal amplitude from the receiver for a period of time, said period of time encompassing the introduction and passage of at least one subsequent pulse in the receiver to stabilize delay of said at least one subsequent pulse in the receiver.   
     
     
       7. The system according to claim 6 wherein the series of pulse trains each comprise a single pulse, the improvement further comprising: means for delaying said single pulse and for synthesizing said at least one subsequent pulse within the transponder.   
     
     
       8. The system according to claim 6 or 7 wherein said gain controlling means comprises a voltage controlled attenuator. 
     
     
       9. The system according to claim 7 wherein said delaying means comprises a surface acoustic wave device.